Temperatures in the southern Italian city of Bari hit 45 degrees Celsius (113 Fahrenheit) on Monday. The heat wave has already sparked two dozen forest fires and put Sicily's renowned lemon trees at risk.
Temperatures at Rome's Ciampino airport registered 36 degrees Celsius (96.8 Fahrenheit) and several Sicilian cities topped 40C (104F). According to Italy's aeronautic weather service, the eastern Sicilian city of Catania registered 44C (111F); Messina 43 (109.4F) and the Sicilian capital Palermo 42 (107.6).
Tourists in Rome tried to cool off in fountains while others took shelter inside air conditioned houses, hotels or offices in a bid to ride out the heatwave.
The civil protection department said the high temperatures and strong winds had fanned 25 blazes in a single day on the islands of Sicily and Sardinia, as well as in the southern mainland regions of Calabria, Abruzzo and Puglia.
Civil protection crews were dousing the blazes from helicopters and other aircraft.
Farm lobby Coldiretti, meanwhile, warned that Sicily's lemons were literally baking in the heat and that farmers were being forced to harvest them unusually early to save them. Coldiretti warned that zucchini, peppers, melons and other fruits and vegetables were also at risk.
It said the produce was particularly vulnerable since it had matured early, thanks to what it said was the warmest spring in two centuries.